If you no longer have access to the Facebook page, but still can see it in your ManyChat account, there is a very quick solution to this problem. Disabling the bot for this page will not help since you don't have sufficient rights to reload this account. What you need to do now is to leave this page. First, click anywhere outside of the "Reconnect Page" window:
After that head to ManyChat Settings --> Users, find yourself in the list of Admins (or other editors/viewers, depending on your role) and click "LEAVE" button. This way you will delete yourself from this bot, and it will be removed from your ManyChat account.
Keep in mind, that at the moment you will not be able to Leave the bot if you are the last Admin on the account, this feature is not yet released for our users. We are still testing it to provide the best experience possible as soon as it’s rolled out for all accounts.